The present invention relates to a monitoring technique for ascertaining the operation status of an apparatus for producing a semiconductor device on the real time basis.
In recent years, production processes of semiconductor devices have become complicated along with miniaturization of the semiconductor devices. Thus, when a defective semiconductor device is produced or when the production yield of a semiconductor device is decreased, it requires a long time to track down the cause of the problem, e.g., to find whether the cause is in a production process or in a production apparatus. Moreover, the process margin in the production of a semiconductor device has been decreasing along with an increase in the integration density of the semiconductor device. As a result, a variation in the production yield of the semiconductor device, which occurs due to an internal error of a production apparatus (process variation among chambers of a multi-chambered production apparatus) or a difference among production apparatuses (process variation among production apparatuses of the same type), has become a great problem. Therefore, in a production process of a highly integrated semiconductor device, a technique for measuring the operation status of a production apparatus on the real time basis, i.e., a technique for monitoring the operation status of a production apparatus, is very important.
Now, a conventional monitoring technique for a semiconductor production apparatus is described while exemplifying a plasma etching apparatus, which is one of typical semiconductor production apparatuses.
FIG. 14 illustrates monitoring of the operation status of the plasma etching apparatus with a conventional monitoring apparatus.
As shown in FIG. 14, the plasma etching apparatus 100 includes a reaction chamber 103 having a lower electrode 102 on which a substrate 101 to be processed is placed. At one side of the reaction chamber 103, a flowmeter (mass flow controller) 104 through which a process gas is supplied into the reaction chamber 103 and a pressure sensor 105 (such as Baratron, or the like) for measuring the gas pressure in the reaction chamber 103 are connected. On the other side of the reaction chamber 103, a vacuum pump 106 for discharging the process gas is connected through a conductance valve (ACP valve) 107. The conductance valve 107 adjusts the amount of the process gas to be discharged. At the bottom of the reaction chamber 103, a high frequency power supply 108 for supplying a high frequency power to the lower electrode 102 is connected through a matcher 109 and an additional sensor 110. Further, a chiller 111 is connected to the bottom of the reaction chamber 103.
Further, the plasma etching apparatus 100 includes a controller computer 112 which is connected through signal lines to the control devices, i.e., the flowmeter 104, the pressure chamber 105, the conductance valve 107, the high frequency power supply 108, the matcher 109, and the chiller 111. The controller computer 112 retains a plurality of pieces of process data acquired from the control devices, such as gas flow rate, gas pressure, degree of valve opening, plasma content value, etc., i.e., the values of a plurality of process parameters which represent the operation status of the plasma etching apparatus 100, in the form of digital data for a certain time period. The controller computer 112 is connected via network to a host computer 10 which manages a plurality of semiconductor production apparatuses including the plasma etching apparatus 100 and a monitoring apparatus (monitoring tool) 20 for ascertaining the operation status of the plasma etching apparatus 100. The monitoring tool 20 acquires a plurality of pieces of process data from the controller computer 112. Note that the sampling rate for the process data in the controller computer 112 is about one second, and thus, a transient variation cannot be observed in parameters of certain types. In order to avoid such inconvenience, the monitoring tool 20 is directly connected through signal lines to the control devices of the plasma etching apparatus 100 (specifically, the flowmeter 104, the pressure chamber 105, the matcher 109, and the additional sensor 110), whereby the monitoring tool 20 can acquire the process data directly from these control devices in the form of analog data.
Next, a conventional monitoring method for a semiconductor production apparatus is described with an example where process data is acquired in the form of analog data directly from the respective control devices of the plasma etching apparatus 100 using the monitoring tool 20 shown in FIG. 14.
FIG. 15 is a flowchart of the conventional monitoring method.
In the first process P1, a plurality of pieces of process data are acquired in the form of analog data directly from the respective control devices of the plasma etching apparatus 100 using the monitoring tool 20, and the acquired process data are retained in a recording medium of the monitoring tool 20.
In the second process P2, the plurality of pieces of process data retained in the recording medium of the monitoring tool 20 are transferred to a recording medium of another computer using a flexible disk, or the like.
In the third process P3, the plurality of pieces of process data are plotted on the time series in the another computer, whereby the trend management of the operation status of the plasma etching apparatus 100 is performed.
In the conventional monitoring method for a semiconductor production apparatus, a variation in each of the process parameter values in the semiconductor production apparatus can be monitored. However, it is necessary for determining whether the operation status of the semiconductor production apparatus is normal or abnormal to observe all of the process parameter values and employ a human (operator) in evaluating the operation status of the semiconductor production apparatus based on the observation result, i.e., all of the process data. That is, in the conventional monitoring technique, evaluation of the operation status of the semiconductor production apparatus cannot be automated. In other words, evaluation of the operation status of the semiconductor production apparatus cannot be performed both objectively and quickly.
In the conventional monitoring method, even when a process recipe consists of a plurality of steps, a statistical value of the process data is not calculated at every step. FIG. 16 shows a monitoring result of the power of a progressive wave of the high frequency power applied to the lower electrode in the etching apparatus shown in FIG. 14. As shown in FIG. 16, one process recipe for the etching apparatus consists of 5 steps, Steps S1 to S5, and the value of the power of the progressive wave is different among the steps. However, in the conventional monitoring method for the semiconductor production apparatus, the statistical value of the process data is not calculated at every step, and therefore, the operation status of the semiconductor production apparatus cannot be accurately ascertained.